Applying special effects methods has been for a long time a working field in the industry. More and more, applications, such as interactive television, or any multimedia applications bring the need of efficient data manipulation.
The invention concerns particularly the merging of different data sets for displaying and the mutual interaction of these different data sets. Namely, in order to improve the interaction between visual data sets, audiovisual data sets or other multi-modal data sets, it is important that some parameters of the different data sets modify the other data sets and among these parameters, the illumination and the reflection.
To result in a realistic or nice looking final image, mutual photometric effects between different visual data sets have to be considered. This is especially true when importing a three-dimensional object in front of a video sequence for instance.
Various methods exist to apply mutual photometric effects to visual data, like shading, specular reflections, cast shadows, mutual illumination.
In film production, professional tools are used to generate photometric special effects off-line. These tools need as input the photometric properties of the visual data as for example light sources or surface reflection properties. Before generating photometric special effects, film production experts recover the photometric properties visually or the photometric properties are measured using measuring tools during film production in the real scene.
In research laboratories, photometric characteristics can be recovered today off-line by automatic algorithms of very high computational cost or by semi-automatic manual interaction.
The off-line or interactive recovering of photometric properties does not allow a real time treatment of the visual data sets for generating photometric special effects.
In the MPEG-7 (MPEG standing for “Motion Picture Expert Group”) proposal n° 99 entitled “An illumination effect descriptor for video sequences”, Stauder proposes to describe illumination properties implicitly by image signal changes for content-based visual information retrieval.
The invention allows a real time treatment of the visual data sets for generating photometric special effects, describing illumination properties in term of light sources for special effect generation.
In a first aspect, the invention proposes a device to generate mutual photometric effects between a plurality of visual data sets, comprising means to position the visual data sets in a common support space characterized in that it comprises:                means for receiving and demultiplexing said visual data sets and photometric parameters respectively associated with said data sets,        means for defining said mutual photometric effects to be generated for these photometric parameters,        composition and rendering means for positioning said visual data sets in said common support space and applying said effects defined for said photometric parameters from at least one of said visual data sets to at least one other of said visual data sets so that at least one visual data set influences one other visual data set in said common support space.        
The invention allows the generation of mutual photometric effects by using the photometric parameters that are transmitted with the visual data sets to be displayed and so can avoid the use of complex devices or methods needed to extract the photometric properties from the visual data sets on the device. In fact the devices that could typically generate mutual photometric effects are low cost devices or consumer products which price has to be reduced. So, it is a great advantage to dissociate this functionality from the device and to provide means to treat the photometric parameters received from an outside terminal.
The means for defining the effects to be generated for the photometric parameters have the capability to define how meta data associated to multimedia data influence other multimedia data. It generates some information called “rendering modi” which represents this influence. This enables the composition and rendering means to display the visual data sets, while applying the photometric effects on these data sets.
The invention is thus particularly interesting in systems providing meta data such as systems providing MEPG-4 coded data and MPEG-7 coded data.
According to a second aspect, the invention proposes a server (Aj) for delivering multimedia data including visual data sets associated with respective photometric parameters for said visual data sets, characterized in that it comprises                means for managing the storage and conditioning of photometric parameters for said visual data sets,        means for transmitting over a transmission link (Cj) said multimedia data bundled with their associated photometric parameters, said multimedia data including means to display at least one of the visual data sets with another of said visual data sets in a common support space.        
This server enables the preparation of photometric parameters to be used for instance with a device according to the first aspect of the invention.
However, this server can be used with any other terminal that would need photometric parameters as input parameters.
This server has the great interest to deliver the multimedia data associated with photometric parameters related to them. This avoids, on a corresponding receiver, the generation of photometric parameters.
According to a third aspect, the invention proposes a multimedia system characterized in that it comprises                at least one server (Aj) according to any of claim 6 to 7 for delivering multimedia data including at least two visual data sets associated with photometric parameters for visual data sets,        means (Cj) for transmitting said visual data sets and their respective photometric parameters bundled together from said server to at least one device according to any of claims 1 to 5,        a device according to any of claims 1 to 5 to generate mutual photometric effects for applying the effects of said delivered photometric parameters of at least one of said delivered visual data sets to at least another of said delivered visual data sets so that said visual data sets influences said other visual data set in a common support space.        
According to a fourth aspect, the invention concerns also a method to generate mutual photometric effects between a plurality of visual data sets, wherein one positions the visual data sets in a common support space, characterized in that:                one delivers multimedia data including at least two visual data sets respectively associated with photometric parameters for visual data sets,        one transmits, bundled together, said visual data sets and their respective photometric parameters to at least one managing means,        one defines dynamically said mutual photometric effects for the photometric parameters and their associated visual data sets,        and one applies said effects defined by said photometric parameters from at least one of said visual data sets to at least another of said visual data sets so that said visual data set influences said other visual data set.        
The invention concerns also a television receiver, a set-top box, or any fixed or mobile terminal having the characteristics of the device to generate mutual photometric effects mentioned above, the advantages of the television receiver, the set-top box, the fixed or mobile terminal being the same as the ones of the device to generate mutual photometric effects.